Substituent-directed oxidation: a simple preparation of γ and δ-lactones by oxidative cyclization of hydroxyalkenes.

Direct Lactonization of Alkenols via Osmium Tetroxide-Mediated Oxidative Cleavage

“…Other methods that have been reported for the conversion of hydroxy olefins to lactones via oxidative cyclization require stoichiometric chromium or permanganate reagents. Schlecht and Kim have used chromium trioxide in acetic acid/acetic anhydride, and Chandrasekaran and co-workers , have used a pentavalent (BiPyH 2 )CrOCl 5 reagent to effect the transformation of various γ- and δ-hydroxy olefins to the corresponding lactones. However, these particular sets of reaction conditions are only useful for hydroxy olefins containing a tertiary alcohol group; otherwise, oxidation of the alcohol to the corresponding carboxylic acid or ketone is a major problem.…”

Metal-Mediated Oxidation of Tertiary Alcohols and Related Fragmentations

“…Treatment of tertiary alcohols of general structure 35 with the Fieser reagent CrO 3 / AcOH/acetic anhydride easily gives lactones with the loss of one carbon atom (Scheme 17). [25] Scheme 17. Oxidative cyclization of γ-and δ-unsaturated tertiary alcohols with the Fieser reagent The role played by the hydroxy group during the process appeared to be essential (when replaced by a methoxy or an acetoxy group, no reaction was observed).…”

“…In an attempt to explain the cyclization process, Schlecht and Kim [25] proposed the mechanism depicted in Scheme 18. It involves the formation of the chromate ester 36, followed by intramolecular oxidation of the double bond, which leads to the chromium(IV) ester 37.…”

An iterative approach to higher polyquinanes

“…The key step in this strategy is the generation of spiro-lactone 7 without the involvement of protective groups as compared to the literature methods. [8][9][10][11][12][13] Treatment of the lactone with methanesulphonic acid-P 2 O 5 mixture generates the enone 8. 14,15 In the last step, the stereochemical control at the ring junctions may be achieved by catalytic cis-addition of the hydrogen to the olefin 8.…”